This invention relates to improved Fischer-Tropsch catalysts containing cerium and their use in CO/H.sub.2 hydrocarbon synthesis in which the catalysts display enhanced reactivity and a reversal of olefin/paraffin selectivity versus traditional non-cerium containing F-T catalysts.
The search for processes to provide alternate feedstocks for chemicals, and particularly low molecular weight olefins, has been prompted by the growing shortage of traditional petroleum reserves, as well as the increasing instability of international hydrocarbon sources.
One approach to the problem has been the utilization of the Fischer-Tropsch synthesis in producing a selective product distribution of olefinic hydrocarbons also containing paraffins, in varying olefin/paraffin ratios, depending on the catalyst composition and reaction conditions. Various catalyst combinations of elements have been tested in the past, of which the chief constituent element has been nickel, cobalt, iron or ruthenium. Secondary products in the processes include branched chain hydrocarbons, aliphatic alcohols, aldehydes and acids.
Ruhrchemie Aktiengesellschaft has disclosed in GB 1,512,743, GB 1,553,361, 1,553,362 and 1,553,363, catalysts pertaining to the selective production of C.sub.2 -C.sub.4 olefins from synthesis gas (preferably carbon monoxide and hydrogen). The inventions embody a process for the production of one or more unsaturated hydrocarbons comprising catalytic hydrogenation of a carbon oxide with hydrogen at 250.degree. C. to below 350.degree. C. and a total pressure of 10 to 30 bars in the presence of a catalyst which contains (a) one or more oxides selected from difficult-to-reduce oxides of metals from Group IVB or a lower oxide of Group V and/or Group VII of the Periodic Table; and (b) one or more metals selected from Group VIII of the Periodic Table, the ratio by weight of the metal or metals of the one or more oxides (a) to the one or more metals (b) being in the range 1:2 to 1:10. Additionally, the catalysts can contain Group IA alkali metal and Zn salt promoter agents. In the process, good yields of unsaturated hydrocarbons, especially gaseous olefins, are reported.
U.K. Pat. No. 833,976 discloses a catalyst for the production of ethylene from CO and hydrogen consisting of four components: the first a group including zinc oxides; the second group preferably being cobalt, although iron also could be used, with the proviso that the Group VIII metal component constitutes not more than 10% of the total weight of the catalyst, and being activated by compounds which may include manganese oxide; the third group including an oxide of titanium and/or the rare earth elements; and the fourth group being a carbonate, oxide or hydroxide of an alkali metal. The reaction preferably is conducted at a temperature of from 350.degree. C. to 520.degree. C., preferably from 350.degree. C. to 450.degree. C.
U.K. Pat. No. 506,064 discloses the preparation of an iron-containing Fischer-Tropsch catalyst. The catalyst also may contain minor amounts of alkali compounds which are practically undecomposed up to 1,000.degree. C. This patent also discloses a lengthy list of other compounds that may be added, including titanium, manganese and cerium oxides or hydroxides.
U.S. Pat. No. 4,199,523 discloses a Fischer-Tropsch catalyst containing at least 60% iron. In addition, promoters such as copper and/or silver and alkali are desirable. Other additives, such as alkaline earth metal compounds, zinc oxide, manganese oxide, cerium oxide, vanadium oxide, chromium oxide, and the like may also be used.
U.S. Pat. No. 4,291,126 discloses a catalytic process for the manufacture of linear saturated alcohols from CO and H.sub.2. The catalyst comprises copper; cobalt; a third metal selected from chromium, iron, vanadium and manganese; a fourth metal which is a rare earth metal; and a fifth metal which is an alkali metal.
U.S. Pat. No. 4,211,673 discloses a catalyst composed of a rare earth metal, such as cerium, and a transition metal, such as iron, for the reduction of CO to produce oxygenated hydrocarbons.
U.S. Pat. No. 4,186,112 also discloses a Fischer-Tropsch catalyst which may include cerium.
Other patents which disclose the use of cerium include U.S. Pat. Nos. 4,162,234; 4,001,317; 3,992,238; 3,932,551; and 3,615,807.
It is desirable to provide a catalyst and/or process for significantly increasing the activity of a low molecular weight olefin producing catalyst while concurrently maintaining a high olefins product slate under standard olefin producing conditions.